When we make decisions based on risk, it matters whether the possibilities are framed in a positive or negative light, what risks are matched to possible benefits. People are likely to opt for 'certain' rather than 'risky' options when only good outcomes are offered, but tempted to make riskier choices confronted with two negative possibilities. This pattern of decision making has always been a bit perplexing because the choices (certain-good, risky-bad) seem to be somewhat contradictory. There are different possible reasons for this (see the paper for more discussion below) - but one theory posits a compromise between desire to make a good decision and desire to minimize cognitive effort, while the other suggests a compromise betweens fears and wishes of an individual.
This recent study found the cognitively 'easy' choice for a certain positive gain matched well with fmri activation data. The negative condition required more brain work under both conditions, and that also showed more imagery area activation (blue arrows) than the simplest positive-certain condition. Imagery, it seems, is very important in making decisions under uncertain conditions.
Analysis and Imagery in Framing Decisions